Not quite. The 1.9L Mi16 came in two versions, DFW (9.5:1) and D6C (10.4:1). The D6C was indeed designed to run on leaded 97 and didn't have a knock sensor at all. At the time, 98 didn't exist.I know I am labouring the point, but its important to get the cause and effect the right way around. It wasn't the higher RON petrol that improved the engine performance, it was because the engine was running on the lower RON petrol that resulted in reduced performance and worse fuel economy. The higher (correct) RON enabled the ECU to characterise the engine to perform as it was originally designed.